1. Field of the Invention
This invention relates to a device for fitting and adjusting an encoder in which, when a rotation shaft of a scanning drum in a drum type image scanning and recording apparatus is joined to a rotation shaft of an encoder through a diaphragm type coupling or the like so that a rotating angular speed of the former may be exactly transmitted to the latter, error in transmission of the rotating angular speed due to deviation of squareness between a flange and a rotation shaft of an encoder itself can be corrected.
2. Prior Art
In a drum type image scanning and recording apparatus, when, for example, a scanning drum on the peripheral surface of which an original picture is mounted and a recording drum on the peripheral surface of which a photosensitive material such as film is mounted, are respectively rotated at a specified angular speed, a reproduced image of said original picture is supposed to be recorded either at full or magnified size on said photosensitive material. For that purpose, the apparatus is usually equipped with a timing signal generating means to control various timings at the time of recording such reproduced image. As one of such means a rotary encoder is connected with each rotation shaft of the scanning drum on the original picture reading side and the recording drum on the recording side thereof through a coupling adapted to the encoder. Accordingly, it is required for such coupling to accurately transmit rotation of the rotation shaft of said drums to a shaft of the encoder.
Generally, when joining a drive shaft such as a rotation shaft of the scanning drum to the rotation shaft of the encoder through a coupling, it is very difficult to connect both rotation shafts coaxially for reasons of machining accuracy of a supporting bracket, flanges, bearings, etc. Hence, as a coupling satisfying the aforementioned requirement even when both rotation shafts are not coaxial (i.e., a coupling enabling transmission of equal angular speed), a so-called diaphram type coupling is widely used. According to such diaphram coupling, even though the rotation shafts of the drum and the encoder are not coaxial, transmission of an equal angular speed is supposed to be possible, so far as it is established that angles .theta..sub.1 and .theta..sub.2 made among axes of the coupling shaft (1), drum rotation shaft (2) and encoder rotation shaft (3) on the same plane (on a paper in this case) are equal to each other as shown in FIG. 4. In such arrangement, however, if the encoder rotation shaft (3) moves a slight distance in the same plane, for example, as shown in two dot chain lines in FIG. 4 .theta..sub.1 ' is not equal to .theta..sub.2 ' (.theta..sub.1 '.noteq..theta..sub.2 ') and the angular speed cannot be transmitted from the drum rotation shaft (2) to the encoder rotation shaft (3).
On the other hand, as shown in FIG. 5, if the drum rotation shaft (2) and the encoder rotation shaft (3) are parallel to each other in the same plane (a paper in this case), the angles made among the axes of the coupling shaft (1), drum rotation shaft (2) and encoder rotation shaft (3) must be .theta..sub.1 =.theta..sub.2, .theta..sub.1 '=.theta..sub.2 ' as shown by the two dot chain lines in FIG. 5 even when aforementioned parallel movement occurs in the same plane, and the equal angle speed can be transmitted from the drum rotation shaft (2) to the encoder rotation shaft (3).
Heretofore, a fitting device of such encoder comprises a bracket (6) fixed to a base (4) and by which an encoder (E) is coaxially fitted to the rotation shaft (2) of a drum (D) at its flange portion (5). This fitting bracket (6) is fixed to the base (4) so that a surface to which the flange portion (5) is fitted is orthogonal to the drum rotation shaft (2). Then, a diaphram coupling (C) is coaxially connected to the drum rotation shaft (2) and fitted to a shaft end portion of an extended shaft (2') having the same diameter as the rotation shaft (3) of the encoder (E) and a shaft end portion of the encoder rotation shaft (3).
Accordingly, unless there is no error at all in the squareness between the fitting surface of the flange portion (5) of the encoder (E) and the rotation shaft (3) thereof, the aforementioned parallel relation is established between the drum rotation shaft (2), i.e., the extended shaft (2') and the encoder rotation shaft (3), and even when there is slight offset between both shafts (2'), (3), transmission of equal angular speed is supposed to be carried out from the drum rotation shaft (2) to the encoder rotation shaft (3).
3. Problem to be Solved
It is true that an equal angular speed is sometimes not transmitted as designed from the drum rotation shaft (2) to the rotation shaft (3) of the encoder (E) fitted on the conventional encoder fitting device. As a result of investigations, it is found that such problem is caused by a slight angle error in the squareness between the fitting surface of the flange portion (5) of the encoder (E) and the rotation shaft (3) thereof. Such error can be corrected by machining the fitting surface of the flange portion (5) on the basis of the rotation shaft (3), but such correction is rather troublesome requiring much labor and time.